Internal shunt and method for treating glaucoma

ABSTRACT

A surgical technique and device wherein an indwelling tube is placed in the eye of a patient having glaucoma. The tube diverts aqueous humor from the anterior chamber to the suprachoroidal space from which it is removed by blood flowing in the choroidal and uveal tissues. This decreases the intraocular pressure.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.11/509,327, filed Aug. 23, 2006, entitled “Internal shunt and method fortreating glaucoma,” which is a continuation of U.S. patent applicationSer. No. 10/429,336, filed May 5, 2003 now abandoned. The subject matterof each of the above-noted applications is incorporated by reference intheir entirety by reference thereto.

FIELD OF THE INVENTION

This invention pertains to a surgical treatment for glaucoma and, moreparticularly, to a new method and apparatus for surgically alleviatingthe intraocular pressure causing the glaucoma condition.

BACKGROUND

Glaucoma is an eye condition in which the hydrostatic pressure withinthe eye is abnormally high, thereby resulting in damage to the opticnerve. There are many treatments for the glaucoma condition that involvelowering the intraocular pressure, either by means of medication orsurgery.

Medicinal treatments either decrease the rate at which aqueous humor ispumped into the eye or improve the outflow of aqueous humor from theeye.

There are three primary surgical methods for treating glaucoma.Presently, none of them are a complete answer to the problem:

-   -   a) Cyclodestructive procedures damage the ciliary body of the        eye and decrease the rate of aqueous humor production. The main        problem is the extremely fine dividing line between too little        and too much treatment. This treatment often does not work, or        it works too well. When the surgery works too well, a hypotonous        eye may develop in which the pressure is too low for normal        ocular function and health.    -   b) Laser therapy of the trabecular meshwork is used to decrease        the resistance of outflow of aqueous humor into the Canal of        Schlemm. The main problem with this procedure is that it only        provides relief for about five years. Re-treatment is often        unsuccessful because it may cause too much scarring of the        outflow channels. Thus, this procedure can do more harm than        good.    -   c) Shunting of aqueous humor from the anterior chamber through        the sclera to outside of the confines of the eye is the most        common surgical procedure. Among the shunting procedures, the        often-performed trabeculectomy is a type of filtering method. It        allows aqueous humor to “filter” out of the eye. A channel is        created from the anterior chamber under a scleral flap to the        episcleral space. The main problem with this procedure is that        the outcome depends on the individual healing properties of the        eye in the post-operative period. Trabeculectomy is often much        less successful in highly pigmented eyes and eyes with previous        surgery, rubeosis, or chronic uveitis. To overcome this problem,        several shunts have been devised to carry aqueous humor from the        anterior chamber to the episcleral space. Scarring often occurs        surrounding the exterior end when shunts are used. This renders        the outcome unpredictable.

Another problem with these types of surgical procedures is that theglobe is left with a transcleral fistula. The fistula renders the eyesusceptible to the ingress of organisms and intraocular infection. Thiscondition is known as endophthalmitis and can be devastating to the eye,since the eye is not naturally designed to defend against this type ofonslaught.

The invention seeks to provide a surgical treatment and apparatus thatwill overcome the many problems associated with present-day surgicalprocedures.

The current invention provides an indwelling shunt that diverts aqueoushumor from the anterior chamber to the blood flowing in the choroidaland uveal tissues. This decreases the intraocular pressure of theglaucomatous eye. The indwelling shunt maintains the area of exposure ofaqueous humor with the uvea by physically preventing scarring of thesurrounding tissues. The method utilizes the normally occurring 25 mm Hgdriving force of the protein colloid osmotic pressure of the blood tomaximize the flow of aqueous humor out of the eye (Yablonski, M. E., Jof Glaucoma, February 2003, 12(1):90-92).

One of the many problems that this inventive procedure overcomes is thenormally low outflow of aqueous humor into the uveal blood caused by thenormally low hydraulic permeability between the aqueous humor of theanterior chamber and the uveal blood vessels (Yablonski, ibid.). Theinternal tube shunt of this invention, however, greatly increases thehydraulic permeability between the aqueous humor and the uveal bloodvessels, thus greatly increasing the magnitude of the outflow via thisroute.

The present invention overcomes the two main objections of most of thecurrent surgical approaches: (a) it requires no permanent transcleralroute for the egress of aqueous humor from the eye, and (b) the successof the procedure is not as dependent on the individual healingproperties of the eye as it is in other procedures. Therefore, theinventive technique not only works in younger eyes, but it also works ineyes of darkly pigmented individuals, and eyes of patients who have hadprevious surgery. In addition, the inventive procedure leaves notranscleral route in the eye, thus decreasing the susceptibility toendophthalmitis.

In an article by Stegmann (1990), a procedure is described wherein anon-penetrating deep sclerectomy is performed. The procedure was called“viscocanalostomy” because a viscoelastic substance was injected intothe cut ends of the canal of Schlemm after the canal was exposed. Likethe present technique, Stegmann first created a thin scleral flap, thencreated a deep sclerectomy by removing the deep sclera, leaving only athin layer of sclera of 50 to 100 microns in thickness overlying thechoroidal tissue beneath.

It should be observed that Stegmann sutured the overlying scleral flapvery tightly, thereby eliminating a final transcleral route for aqueoushumor drainage. This implied that the intended mechanism for aqueoushumor egress was an intraocular shunt. The mechanism of action of theprocedure was proposed by Stegmann to be the access of aqueous humor tothe newly dilated canal of Schlemm, from which it flowed from the eye bythe usual outflow routes. However, if this were the case, the outflowfacility of the eyes should be increased, as measured by tonography. Nostudies have shown an increase in outflow facility after theviscocanalostomy is performed, despite a marked decrease in intraocularpressure.

Another related technique to that of the current invention is theprocedure that sutures a collagen implant beneath the scleral flap intothe bed of the deep sclerectomy (M. E. Karlen, E. Sanchez, C. C.Schnyder, M. Sickenberg, and A. Mermoud, Deep sclerectomy with collagenimplant: medium term results, Br J Ophthalmol, January 1999,83(1):6-11). The method provides a non-penetrating deep sclerectomywherein a collagen implant is placed between the overlying scleral flapand the underlying suprachoroidal space. No dilation of the canal ofSchlemm is performed. No flow of aqueous humor into the uveal blood issuggested, and only two scleral flap sutures are used, which renders thescleral flap permeable to transcleral flow and creates a transcleralfistula.

In U.S. Pat. No. 6,383,219, issued on May 7, 2002 to Telandro et al., arelated non-penetrating deep sclerectomy is illustrated. The method usesan implant made of a cross-linked hydraluronic acid material, which isshaped like a polyhedron having at least five faces. The material isplaced between the overlying scleral flap and the underlyingsuprachoroidal scleral bed. Unlike the current inventive method, thisprocedure does not propose that the aqueous humor flows mainly into theadjacent uveal blood in response to its protein colloid osmoticpressure. The use of only two sutures in the overlying scleral flaprenders this flap permeable to transcleral flow, creating a transcleralfistula.

The stated mechanism for relief in Telandro et al. is the high watercontent that acts like a wick, i.e., it transports the ocular fluids bycapillary action. No mention is made of flow of aqueous humor into theuveal blood, and it is implied that the final destination of the flow ofaqueous humor is across the overlying scleral flap into the episcleralspace. This method is similar to a conventional trabeculectomy and otherfiltering procedures.

Some internal shunts have previously been proposed. In U.S. Pat. No.6,450,984, issued to Lynch and Brown on Sep. 17, 2002, a shunt isillustrated that shunts fluid from the anterior chamber. The shunt isplaced under a scleral flap and into the open ends of the canal ofSchlemm. This method requires normal drainage of aqueous humor from thecanal of Schlemm into the episcleral veins. Since in open angleglaucoma, which is the most common type of glaucoma, flow through thecanal of Schlemm is impaired, this technique appears flawed. To the bestof knowledge and belief, no reports exist in the literature depictingthe successful implementation of this technique.

In U.S. Pat. No. 5,601,094, issued on Feb. 11, 1997 to Reiss, a shunt isdescribed which causes flow of aqueous humor from the anterior chamberto the suprachoroidal space. Unlike the present invention, however, theshunt is exteriorized before it enters the suprachoroidal space. Thisrenders the eye susceptible to endopthalmitis. To the best of knowledgeand belief, there have been no successful reports for this technique inthe literature.

In U.S. Pat. No. 4,521,210, issued on Jun. 4, 1985 to Wong, a shunt isillustrated that extends from the anterior chamber to the suprachoroidalspace. The shunt is designed to create a permanent cyclodialysis cleftand shunt aqueous fluid to the suprachoroidal space from the anteriorchamber. The suprachoroidal space is surgically entered and the ciliarybody disinserted from the scleral spur. To the best of knowledge andbelief, there have not been any reports in the literature of the successof this technique.

SUMMARY

In accordance with the present invention, a surgical technique andapparatus are illustrated for alleviating the glaucoma condition. Thecurrent invention provides an indwelling shunt that diverts aqueoushumor from the anterior chamber to the blood flowing in the choroidaland uveal tissues. This decreases the intra-ocular pressure. Theindwelling shunt maintains the area of exposure of aqueous humor withthe uvea by physically preventing scarring of the surrounding tissues.The method utilizes the 25 mm Hg driving force of the protein colloidalosmotic pressure of the blood to maximize the flow.

One method illustrated in FIGS. 1, 3, and 4 comprises the initial stepof folding back a one-third scleral thickness scleral flap hinged at theperipheral cornea. A small cavity is generated, extending into theperipheral cornea, by the removal of deep scleral tissue (known as adeep sclerectomy), leaving a very thin, approximately 50 micron inthickness scleral bed (FIG. 4) over the underlying choroid. Thesuprachoroidal space is entered at the lateral edges of the scleral bedby cutting directly or at a laterally slanted angle. The shunt, whichcan comprise a precut tube with polished edges, is placed one endpermanently into the suprachoroidal space and the other in the sclerallake and is sutured into the overlying sclera. The precut tube can bedelivered with a suture in place for ease of deployment. Other examplesof structures that can function as a shunt in addition to a hollow tubeinclude a solid section of material grooved to carry aqueous humor, or astructure of open cell foam or other porous material, and similarstructures in each case made from biologically compatible materials.

After suturing, one end of the tube is in the suprachoroidal space andthe other is in the scleral lake created by the deep sclerectomy. Then atrabeculectomy specimen is created, plus a peripheral iridectomy, as ina standard trabeculectomy. The scleral flap is turned back to its normalposition resting on the deep scleral shelf and is sutured to theadjacent sclera with six to ten interrupted sutures to yield a tightclosure. The shunt can be fabricated from silicone or otherbiocompatible materials. One or two such tubes can be placed on eachlateral side of the deep sclerectomy. These tubes not only shunt aqueoushumor from the scleral lake into the suprachoroidal space, they alsohelp maintain the volume of the scleral lake by acting as a physicalbarrier between the overlying scleral flap and the underlying scleralbed.

In another version of this procedure (FIG. 2), the scleral lake issmaller and is separated from the anterior chamber by an approximately 3mm wide layer of full thickness sclera. A tunnel is created with a 23gauge needle and one end of the tube is inserted through the tunnel intothe anterior chamber. The other end of the tube is placed through anincision, at the posterior edge of the scleral bed, into the posteriorsuprachoroidal space where it is sutured to the overlying sclera. Thenthe scleral flap is tightly sutured back into place. Other examples ofstructures that can function as a shunt in addition to a hollow tubeinclude a solid section of material grooved to carry aqueous humor, or astructure of open cell foam or other porous material, and similarstructures in each case made from biologically compatible materials.

It is an object of this invention to provide an improved surgicaltechnique and apparatus for treating glaucoma.

It is another object of the present invention to provide both a surgicalmethod and an apparatus that utilizes the uveal blood vessels to drainaqueous humor from the anterior chamber of the eye to decreaseintra-ocular pressure in the treatment of glaucoma.

BRIEF DESCRIPTION OF THE DRAWINGS

A complete understanding of the present invention may be obtained byreference to the accompanying drawings, when considered in conjunctionwith the subsequent detailed description, in which:

FIG. 1 illustrates a top, three-dimensional, perspective, enlarged viewof a portion of the eye, shown in partial cut-away;

FIG. 2 depicts a top, three-dimensional perspective view of the secondtype of internal tube shunt procedure, enlarged view of the portion ofthe eye, shown in partial cutaway;

FIG. 3 shows a top view of the portion of the eye illustrated in FIG. 1;and

FIG. 4 illustrates a sectional view of the portion of the eye depictedin FIGS. 1 and 3.

For purposes of brevity and clarity, like components and elements of theapparatus of this invention will bear the same designations or numberingthroughout the FIGURES.

DETAILED DESCRIPTION

Generally speaking, a surgical technique and apparatus is describedwherein an indwelling shunt is placed in the eye of patients havingglaucoma. The shunt diverts aqueous humor from the anterior chamber tothe suprachoroidal space from which it is removed by the blood flowingin the choroidal and uveal tissues. This decreases the intra-ocularpressure. The indwelling shunt maintains the area of exposure of aqueoushumor with the uvea by physically preventing scarring of the surroundingtissues. The method utilizes the 25 mm Hg driving force of the proteincolloidal osmotic pressure of the blood to drive aqueous humor into theblood.

In FIGS. 1 through 4, a portion of an eye is shown being surgicallyprepared with a hollow tube (indwelling shunt) 1 for the treatment ofglaucoma. The hollow tube 1 has an interior open space 2 in which fluid(not shown) is transferred. The tube 1 diverts aqueous humor from thescleral lake 8 (FIG. 4) to the suprachoroidal space 12, as best observedwith reference to FIGS. 1 and 3. This shunting of the aqueous humordecreases the intra-ocular pressure. The indwelling shunt 1 maintainsthe area of exposure of aqueous humor with the uvea by physicallypreventing scarring of the surrounding tissues. The method utilizes the25 mm Hg driving force of the protein colloidal osmotic pressure of theblood of the uveal blood vessels 14 to maximize the flow (Yablonski,ibid.).

The method comprises the initial step of folding back the scleral flap 4of the eye (FIG. 1). A small cavity, the deep scleral lake 8, isgenerated by the removal of tissue in the sclera 7. The suprachoroidalspace 12, a normally occurring potential space, is entered by cuttingdirectly, or at a slanted angle through the scleral bed 9. The shunt 1,which can comprise a precut tube with polished edges, is then insertedinto the suprachoroidal space 12 and sutured by sutures 15 to theoverlying sclera 7 therein, as best seen in FIGS. 1 and 2. The precuttube 1 can also contain sutures fabricated in place for ease ofdeployment.

After suturing the tube 1 in place, a trabeculectomy specimen 5 may beremoved, thus creating a direct communication to the anterior chamber 21(best seen in FIG. 4). A peripheral iridectomy 6 may be created in theiris 11. The scleral flap 4 is then replaced, resting on the deepscleral shelf 3 where it is tightly sutured to the adjacent sclera 7.The shunt 1 can be fabricated from silicone or other biocompatiblematerials. It can be seen, therefore, that this technique does notcreate a permanent cyclodialysis cleft and does not disinsert theciliary body from the scleral spur.

Referring to FIG. 1, the internal tube shunt 1 of the present inventionis inserted and sutured between the suprachoroidal space 12 and the deepscleral lake 8 generated by the surgical forming of a scleral flap 4,and a deep sclerectomy starting 4.5 mm from the limbus and extendinginto the peripheral cornea 10. Since the deep sclerectomy is about 1 mmsmaller than the dimensions of the scleral flap 4, a deep scleral ledge3 approximately 0.5 mm in width is created on the lateral and posterioraspect of the deep scleral lake 8.

Referring now to FIG. 2, the shunt 1 of the present invention isillustrated passing from the anterior chamber 21 through the adjacentsclera 7, through a posterior deep scleral lake 8, and into theposterior suprachoroidal space 12 where it is sutured to the overlyingsclera 7. The deep scleral lake 8 is generated by forming a scleral flap4 and deep sclerectomy similar to that of FIG. 1 but with an anteriorend 3 mm posterior to the cornea 10.

Referring now to FIG. 3, the shunt 1 of the present invention isinserted and laterally sutured into the suprachoroidal space 12 on eachside of the deep scleral lake 8 generated by forming a scleral flap 4and a deep sclerectomy, with the scleral flap 4 sutured back into placeover the ends of the tube shunts 1. Also shown are the peripheraliridectomy 6 and the trabeculectomy site 5.

Referring to FIG. 4, the shunt of this invention is seen in the deepscleral lake 8 between the overlying scleral flap 4 and the underlyingscleral bed 9. Also shown are the trabeculectomy site 5 and theperipheral iridectomy 6.

FIGS. 1, 3, and 4 show one possible incorporation of the invention whereaqueous humor gains access to the shunt 1 via a trabeculectomy 5 betweenthe anterior chamber 21 and the deep scleral lake 8 where one end of thetube 1 lies. From the deep scleral lake 8, aqueous humor is shunted viathe tube 1 to the suprachoroidal space 12.

FIG. 2 shows another possible incorporation of the invention in whichaqueous humor is shunted directly by a tube 1 that passes from theanterior chamber 21 through the sclera 7 between the anterior chamber 21and the deep sclerectomy space, and into the suprachoroidal space 12 atthe posterior aspect of the deep sclerectomy where it is sutured to theoverlying sclera 7.

In this version, the deep sclerectomy is smaller than the deep sclerallake 8 shown in FIGS. 1 and 4. Unlike the version in FIGS. 1 and 4 wherethe deep scleral lake 8 serves as the pool of aqueous humor which flowsinto the tube 1, in the version of FIG. 2, the deep sclerectomy servesonly to allow the surgeon access for insertion of the tube 1 into theanterior chamber 21, anteriorly, and the suprachoroidal space 12,posteriorly. After the tube 1 is in place, the scleral flap 4 is suturedto the adjacent sclera 7 and no permanent deep scleral lake 8 needpersist.

Since other modifications and changes varied to fit particular operatingrequirements and environments will be apparent to those skilled in theart, the invention is not considered limited to the examples chosen forpurposes of disclosure and covers all changes and modifications which donot constitute departures from the true spirit and scope of thisinvention.

Having thus described the invention, what is desired to be protected byLetters Patent is presented in the subsequently appended claims.

What is claimed is:
 1. A method of treating glaucoma, comprising:providing an elongated tube comprising at least one inflow port, atleast one outflow port and an internal fluid passageway communicatingbetween the at least one inflow port and at least one outflow port;creating a tunnel in eye tissue; inserting the tube through the tunnel;positioning the tube entirely within an interior of the eye such thatthe at least one inflow port of the fluid passageway is positioned inand communicates with the anterior chamber and the at least one outflowport of the fluid passageway communicates with the suprachoroidal space;leaving only the tube inside the eye; and diverting aqueous humorthrough the fluid passageway from the anterior chamber toward thesuprachoroidal space.
 2. A method as in claim 1, wherein implanting thetube entirely within an interior of the eye comprises implanting thetube so that the tube is positioned radially inward of an outer surfaceof the sclera.
 3. A method as in claim 1, wherein implanting the tubeentirely within an interior of the eye comprises implanting the tube sothat at least one inflow port is positioned in the anterior chamberposterior of an inner surface of the cornea.
 4. The method of claim 1,wherein the tube comprises a rounded, outer surface that contacts aportion of the sclera.
 5. The method of claim 1, further comprisingattaching a retaining structure to an end of the tube.
 6. The method ofclaim 5, wherein the retaining structure comprises a suture attached toa distal end of the shunt.
 7. The method of claim 1, further comprisingcutting the tube prior to implantation.
 8. A method of treatingglaucoma, comprising: providing a tube having an internal lumen, a firstopening for fluid to flow into the internal lumen, and a second openingfor fluid to flow out of the internal lumen; creating a tunnel in eyetissue; inserting the tube through the tunnel; positioning the tubeinside an eye so that the first opening is inside the anterior chamberand the second opening communicates with the suprachoroidal space;leaving only the tube inside the eye; and causing fluid to flow from theanterior chamber into the internal lumen through the first opening andout of the internal lumen toward the suprachoroidal space through thesecond opening.
 9. A method as in claim 8, wherein positioning the tubeinside an eye comprises implanting the tube so that the tube ispositioned radially inward of an outer surface of the sclera.
 10. Amethod as in claim 8, wherein implanting the tube inside an eyecomprises implanting the tube so that the first opening is positioned inthe anterior chamber posterior of an inner surface of the cornea. 11.The method of claim 8, wherein the tube comprises a rounded, outersurface that contacts a portion of the sclera.
 12. The method of claim1, wherein the tunnel is created using a needle.
 13. The method of claim1, wherein the outflow port is positioned in the suprachoroidal space.14. The method of claim 1, wherein the tube is cylindrical.
 15. Themethod of claim 1, wherein aqueous humor flows directly into thesuprachoroidal space via the fluid passageway.
 16. The method of claim8, wherein the tunnel is created using a needle.
 17. The method of claim8, wherein the second opening is positioned in the suprachoroidal space.18. The method of claim 8, wherein the tube is cylindrical.
 19. Themethod of claim 1, wherein aqueous humor flows directly into thesuprachoroidal space via the internal lumen.